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About Joy

Joy is a purely functional programming language that was produced by Manfred von Thun of La Trobe University in Melbourne, Australia. Joy is based on composition of functions rather than the lambda calculus. It was inspired by the function-level programming style of John Backus's FP.

Inception: 2001

Forthinfluenced by Schemeinfluenced by FPinfluenced by

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Contents

Overview

Functions in Joy lack formal parameters, instead functions implicitly operate on a stack. For example, a function that squares a numeric input can be expressed as follows:

DEFINE square == dup * .

The square function makes a copy of the top element with dup, and then multiplies the two top elements of the stack with *, leaving the square of the original top element at the top of the stack, with no need for a formal parameter. This makes Joy concise, as illustrated by this definition of quicksort:

DEFINE qsort ==

[small]

[]

[uncons [>] split]

[swapd cons concat]

binrec.

Mathematical purity

Joy is a concatenative programming language: "The concatenation of two programs denotes the composition of the functions denoted by the two programs".

Article from Wikipedia (CC BY-SA 4.0), where it is maintained by volunteer editors.

Notable quotes

“And these are joys, like beauty, but skin deep.”
— Philip James Bailey, Festus (1813), scene A Village Feast, line 26.
“Verily it is the most joy that may be, as to my sight, that He that is highest and mightiest, noblest and worthiest, is lowest and meekest, homeliest and most courteous: and truly and verily this marvellous joy shall be shewn us all when we see Him.”
— Julian of Norwich, Revelations of Divine Love (c. 1393), Chapter 7.
“The joys of heaven are not the joys of passive contemplation, of dreamy remembrance, of perfect repose; but they are described thus: "They rest not day nor night. His servants serve Him, and see His face."”
— Alexander Maclaren, Dictionary of Burning Words of Brilliant Writers (1895), p. 307.
“Forgive me, Spirit of my spirit, for this, that I have found it easier to read the mystery told in tears and understood Thee better in sorrow than in joy; that, though I would not, I have made the way seem thorny, and have wandered in too many byways, imagining myself into moods which held Thee not.”
— George William Russell, in his Preface to Collected Poems (1913).
“Gaudia non remanent, sed fugitiva volant.”
— Joys do not stay, but take wing and fly away.
“If a man is dying for want of bread, and you give him bread, is that to make him gloomy? That is what Christ is to the soul — the Bread of Life. You will never have true pleasure or peace or joy or comfort until you have found Christ.”
— Dwight L. Moody, p. 356.

Quotes via Wikiquote (CC BY-SA), each with its original source.